1. Field
Embodiments relate to optimization of the copying of change recorded data by using spare flash capacity.
2. Background
A storage controller may be coupled to one or more of a plurality of hosts. The storage controller may manage a plurality of storage devices, such as disk drives, tape drives, flash drives, etc., that are coupled to the storage controller. The plurality of hosts may access data stored in the storage devices via the storage controller.
Host applications that execute in the plurality of hosts may create logical storage volumes, and subsequent to the creation of the logical storage volumes write to logical addresses of the logical volumes. The host applications may also read from logical addresses of the logical storage volumes.
The storage controller assigns physical storage to store data that is stored in the logical storage volumes. For example, the storage controller may assign one or more physical extents to each logical storage volume, where the physical extents may reside in storage devices (such as nearline storage, disk drives, tape drives, flash drives, etc.) coupled to the storage controller. Latency is the time interval between initiating a query, transmission, or process, and receiving or detecting the results, often given as an average value over a large number of events. The storage devices attached to or controlled by a storage controller may have different latencies. In general, a flash storage may have a lower latency than a disk storage or a nearline storage.
A point-in-time copy is a fully usable copy of a defined collection of data that contains an image of the data as it appeared at a single point in time. The copy is considered to have logically occurred at that point in time, but certain mechanisms may perform part or all of the copy at other times. A source volume and a target volume may be referred to be in a point-in-time copy relationship, if the target volume is a point-in-time copy of the source volume.